1. Field of the Invention
The invention herein relates to sealing devices for sealing rotating shafts. More particularly it relates to a cartridge assembly incorporating a plurality of sealing means in a unitary assembly for use with.
2. Description of the Prior Art
The invention herein is a sealing cartridge specifically designed for the sealing of rotating shafts such as the shafts of centrifigal pumps, sheaves, roller shafts, motor shafts and the like. (For brevity, the particular device having the shaft to be sealed will hereinafter be referred to as a pump. It will be recognized, however, that the pump is selected only as a typical example and that the invention is applicable to many other devices having rotating shafts.) In each case the pump contains a fluid on the interior. The function of the sealing device is to permit the rotating shaft to penetrate the wall of the pump casing while yet retaining the fluid on the interior thereof.
Sealing cartridges have been known in the past for use with reciprocating shafts. For instance, U.S. Pat. Nos. 2,443,332; 2,565,923 and 3,224,817 all show cartridge units intended to seal reciprocating piston rods. Each of these devices comprises interior mechanical packings (illustrated as chevron packings) and an exterior wiper ring. The wiper ring is a non-pressure element and serves no sealing function. Rather its purpose is to wipe off that foreign matter which accumulates on the exterior of the unit rod and prevent its being drawn into the interior of the seal on the inward stroke of the rod. In addition it wipes off that fluid passing the mechanical packings and flowing down the piston rods. In the particular device shown in U.S. Pat. No. 2,443,332, the wiper rod also serves to direct the accumulated fluid into a channel for recovery and reuse.
Such devices are not applicable to use with rotating shafts, however. Since reciprocating rods must be lubricated along a significant portion of their length, sealing elements for reciprocating rods are designed to permit a controlled amount of fluid leakage past the sealing element. This is a significantly different concept of sealing than that required for rotating shafts, where complete fluid containment is desired. In the past where compressed mechanical packings were used on rotating shafts, some degree of leakage was required in order to maintain proper lubrication of the seals. This, of course, prevented the attainment of the goal of complete field containment. On the other hand, use of pressure lip seals, while achieving complete fluid containment, presents serious difficulties of replacement when worn and permits sudden massive leakage upon seal failure. Seal designers have been forced to resort to such complex expedients (such as the plurality of staggered seals engaging notched bearings shown in U.S. Pat. No. 3,773,336) in an attempt to simplify seal replacement and to permit greater seal service life.
In addition, such mechanical packings and radial pressure lip seals which have been used in the past have always been individually handled and mounted, requiring a great deal of precise hand cutting and fitting to obtain a satisfactory seal.